Magnetizer



July 1, 1941. R. A. BRADER MAGNETIZER Filed Jan. 5, 1940 Patented July1, 1941 2,247,745 MAGNETIZEB Ralph A. Brader, Bloomfield, N. 1.,assignor to Western Electric Company, Incorporated, New York, N. Y., acorporation oi. New York Application January 5, 1940, Serial No.'312,498

12 Claims.

This invention relates to magnetizers, and. more particularly tomagnetizing apparatus for use in the production or permanent magnets.

An object of this invention is the provision of improved apparatus forsubjecting articles to a magnetizing force of suitable characteristicsfor producing in the articles a high degree of permanent magnetism.

Permanent magnets employed in communication apparatus and in other typesof equipment are produced in various shapes and sizes depending upontheir intended field of service. Many of these types can be magnetizedreadily by placing them between the poles of a powerful -electromagnetor, in some instances, a strong permanent magnet. However, certainmagnet types have a configuration, or possibly a very small air gap,which precludes the possibility of employing another magnet forproducing the ma netizing fiux.

In such cases it is usually possible to place a temporary winding aroundthe article to produce the desired magnetization. To minimize the costof this operation, or because of the shape 01 the magnet, it is oftendesirable to use as few turns in the temporary winding as possible andto secure the ampere-turns necessary for the degree of magnetizationdesired by use of a very large current. The duration of the current isnot particularly important from a prodof the article occurs almostinstantaneously when the current is applied. However, the duration oithe current is highly important from a cost standpoint because oi thesize and nature oi the circuit, switches and other equipment needed tohandle currents of this magnitude ior any appreciable period of time.

It is, therefore, desirable to produce a very high direct current for avery short period of time in the temporary winding on the magnet. Itis-difllcult to use conventional direct current supply sources, such asa high-voltage battery or a large capacity generator, for this purpose.The circuit and control equipment necessary for handling currents of thedesired magnitude from these sources are either not very suitable -forlarge scale production or tend to be costly and somewhat dangerous tooperate when adapted to large scale production.

One embodiment of this invention provides an inexpensive apparatus thatcan be used without hazard for producing and applying a very large andefilcient magnetizing current in a coil containing the article. In thisapparatus alternat- 85 provide the desired capacity.

ing current from a conventional source is rectified and employed tocharge a condenser. The condenser is then discharged through a mercuryvapor unidirection switch and through a mag- 55 netizing coil around thearticle to induce a magnetic field in the article. To provide for abruptdischarge of the condensers, the mercury switch is actuated through anignitor circuit which vaporizes the mercury and is fed irom thecondenser. To prevent oscillation in the condenser discharge circuit,and resultant partial demagnetization oi the article, means are providedto permit fiow of current only in one direction between the condenserand magnetizing coil. To

'15 insure safe operation of the apparatus, the condenser is charged anddischarged in separate circuits and a switch common to both circuitsprevents the operation of one circuit at any time the other circuit isclosed.

Following is a more complete description of the invention taken inconjunction with the appended drawing in which the single figure is aschematic drawing showing a magnetizing apparatus embodying certainfeatures of the invention.

The apparatus shown in the drawing is adapted ior magnetizing an articleIt by passing a current 0! suitable characteristics through a wire I Ilooped or wrapped around the article. In some 310 cases a coil intowhich the article is inserted may not quality standpoint becausemagnetization be used instead of the wire loop.

The magnetizing current is supplied from a condenser H, or moreconveniently from a plurality of condensers connected in parallel to Thecondensers are charged and: then discharged through the wire loop orcoil by means of a condenser charging circuit and a condenserdischarging circuit under control of a switch common to both cir- 40cuits.

Current for the apparatus is conveniently secured from a conventionalalternating current supply source H to which a pair of power lead wiresl4 and I5 are connected, one of the leads having a manually operatedcontrol switch I6 therein.

Operation of the condenser charging and discharging circuits iscontrolled by means of a circuit selecting relay or solenoid having aspring 5 l1 depressed pivoted armature l8 adapted to alhaving a pushbutton-switch 24 therein, and a means of a wire 30. The filament of therecti-v fler tube is heated by means of a transformer 3| connectedacross the power leads and the filament is connected to the left handcontact 20 in the circuit selecting relay through a wire 32. A wire 33-runs from the relay armature to one terminal of the condenser and theother terminal of the condenser is connected to the variable transformersecondary through a wire 35 and a resistance 31. Thus, the condensercharging series circuit includes the transformer secondary, rectifyingtube, circuit control relay, condenser and resistance.

As stated above, the condenser is discharged through a loop or coilaround the article. Be-

cause this combination has both resistance and inductance, the dischargecurrent normally tends to oscillate with a steadily decreasingamplitude. Under these conditions the magnet would be magnetized duringthe first half current cycle and then partially demagnetized during thenext negative half cycle and the final magnetic rating of the articlewould be inadequate. To avoid this contingency, means are provided todischarge the condenser through the wire loop th'en closing thedischarge circuit.

without any oscillation in the condenser dis charge circuit.

The condenser is discharged through an evacuated mercury vapor tube 30which acts as a mercury vapor rectifier and passes current, in

only one direction; The tube is normally nonconducting and is actuatedor. fired to become instantaneously and unidirectionally conducting whenmercury contained in the tube is vaporized by the application of currentto an electrode'll in the tube. Thus thetube acts as a unidirectionalswitch to cause discharge of the condenser. These tubes are availablecommercially and the fIgnitron" tube is suitable for this purpose.

The anode of the tube is connected to one terminal of the condenserthrough wires 30 and I4.

The cathode of the tube is connected through a wire 40 to one end of thewire loop around the magnet. The other end of the wire loop is.

connected by means of wires 4| and 85 to the other terminal of thecondenser. This arrangement provides a series circuit running from thecondenser, through the mercury vapor switch, and through the wire looparound the magnet.

The mercury vapor switch is fired or ignited by current supplied fromthe condenser. In the firing or i'gnitor circuit the right hand contactis in the circuit selecting relay is connected by wires ll, 44 and 48through a rectifying tube 46 and resistance 41 to the ignitor electrode48' in the tube. The'rectifying tube, which is heated by a transformer50 supplied with current from the power leads through wires SI, 25 and22, prevents any oscillation in the magnetizing circuit through theignitor circuit by permitting current to flow only in the direction fromthe condenser to the ignitor electrode.

As a further precaution against oscillation in the magnetizing coll. aresistance is connected across the magnetizing coil or loop to suppressproaches full discharge, to a value below the inverse voltage rating ofthe tube.

In the operation of the apparatus the magnetizing loop or coil is firstplaced around the article to be magnetized. At this time the condenserdischarge circuit is closed, and the charging circuit is open becausethe circuit selecting relay armature is normally positioned against theright hand relay contact. After the article is positioned, the pushbutton is closed which shifts the relay armature to the left handcontact. This action first opens the discharge circuit and then closesthe charging circuit to charge the condenser.

To facilitate control of the apparatus a signal lamp is provided toindicate the condition of the condenser. This lamp is connected acrossthe power'leads through wires 58 and il2l through the contacts of 'anormally open solenoid Bl in a by-pass circuit around the condenser. In

the by-pass circuit is a resistance 59 of such rating to cause thesolenoid to close and the lamp to glow whenever current is flowing inthe charging circuit or a charge of predeterers.

The condenser charge builds up rapidly when the charging circuit iscompleted, causing the signal lamp to glow. The push button isthenreleased, which permits the circuit selecting re lay armature to move tothe right handcontact, thereby first opening the charging circuit andWhen the discharge circuit is closed, the condenser potential is appliedto the lgnitor electrode, which has a very high resistance, through theignitor circuit.

the condensers to a potential of ,500 volts. Cur-" rent values as highas 25,000 amperes can be employed. By' subjecting the article tocurrents of this magnitude and applying the current in an abrupt impulsewithout oscillation in the discharge circuit, a magnetic fieldis-induced in the article to establishpermanent magnetization therein atmaximum values.

Due to the construction'of the apparatus, the hazards normally attendingthe use ofheavy currents are eliminated. At the time the operatorconnects the article to the apparatus, the

condenser discharge circuit is closed and the condenser is dischargedbecause of the normal position of the armature in the circuit selectingrelay. If the relay should be defective and the armature be deflectedfrom its normal position no current can flow in the-discharge circuitbecause the charging and discharging circuits cannot be operatedsimultaneously.

It will be apparent that various modifications and adaptations of theabove described apparatus are feasible and it is to be understood hatThis vaporizes some of the mercury tov .make the tube conducting andcurrent then flows the invention is limited only by the scope of theappended claims.

What is claimed is:

1. In an apparatus for producing an electrical impulse of short durationand magnetizing an article therewith, a condenser, a charging circuitfor the condenser, a source of current for said circuit, and a dischargecircuit for the condenser. said discharge circuit comprising a coilaround the article, and means actuated by the condenser charge fordischarging the condenser through the coil in a single unidirectionalimpulse to induce a magnetic field in the article.

2. In an apparatus for magnetizing an article, a condenser, a circuitfor charging the condenser, a source of current for said circuit, adischarge circuit for the condenser, means in the discharge circuitresponsive to the charge on the condenser to cause the condenser todischarge into the circuit in an abrupt unidirectional impulse, andmeans ,in the discharge circuit for subjectin the article to saidimpulse to induce a magnetic field in the article and magnetize thearticle.

3. In an apparatus for magnetizing an article, a condenser, a condensercharging circuit, a condenser discharging circuit, a coil in thedischarg- "ing circuit positioned to cause the condenser discharge toinduce a magnetic field in the article, means in the discharge circuitactuated by the condenser charge to cause discharge of the condenserinto the coil in an abrupt unidirectional impulse, and means foroperating the condenser charging and discharging circuits independently.

4. In an apparatus for producing an abrupt and unidirectional electricalimpulse for inducing a magnetic field in an article and permanentlymagnetizing the article. a condenser, a. condenser charging circuit, asource of current for said condenser charging circuit, a dischargecircuit for the condenser, a coil in the discharge circuit surroundingthe article, means in said discharge circuit to discharge the condenserthrough the coil, said means being responsive to the condenser charge,and a control switch for the charging and discharging circuits, saidswitch being adapted to close the charging circuit only when thedischarging circuit between the condensers and coil is open.

5. In an apparatus for magnetizing an article, a coil around thearticle, a condenser, a circuit for charging the condenser, a circuitfor discharging the condenser through said coil, a mercury vapor switchin the discharging circuit, said switch having an 'electrodethereinadapted to vaporize the mercury when energized and make the switchunidirectionally conducting, and means for discharging the condenser byapplying current from the condenser to the electrode in the mercuryvapor switch.

6. In an apparatus for magnetizing an article, a coil around thearticle, a condenser, a circuit for charging the condenser, a circuitfor discharging the condenser through said coil,.said condenserdischarging circuit comprising a mercury vapor rectifier connected inseries with the condenser and coil and having an ignitor electrodetherein to cause vaporizing of the mercury when current is appliedthereto, an ignitor circuit connecting the condenser and the electrode,and a rectifier tube in the ignitor circuit to permit the flow ofcurrent in the ignitor circuit only in the direction from the condenserto the electrode.

7. In an apparatus for magnetizing an article, a coil around thearticle, a condenser, a circuit for charging the condenser, a mercuryvapor switch connected in series with the condenser and coil and havingan ignitor electrode therein for vaporizing the mercury and making theswitch unidirectionally conducting when current is applied to theelectrode, an ignitor circuit connecting the condenser and electrode forsupplying currentto the electrode from the condenser, and a manuallycontrolled switch between the condenser charging circuit and the ignitorcircuit for selectively operating said circuits to charge the condenserand then discharge the condenser by applying current from the condenserto the ignitor electrode in the mercury vapor switch.

8. In an apparatus for magnetizing an article, a coil around thearticle, a condenser, a circuit for charging the condenser, a mercuryvapor switch connected in series with the condenser and coil and havingan ignitor electrode therein for vaporizing the mercury when current isapplied to the electrode, an ignitor circuit for conducting current fromthe condenser to the ignitor electrode, and a second switch forsimultaneously controlling both the condenser charging circuit and theignitor circuit, said second switch being adapted to permit current toflow from the condenser to the ignitor electrode in the mercury vaporswitch only when .the condenser charging circuit is open.

9. In an apparatus for magnetizing an article, a coil around thearticle, a condenser, a circuit for charging the ,condenser, a mercuryvapor switch connected in series with the condenser and coil andcontaining an ignitor electrode for causing the mercury to vaporize whencurrent is applied to the electrode, an ignitor circuit connecting thecondenser andelectrode forsupplying current to the electrode, arectifying tube in the ignitor circuit to permit the flow of current insaid circuit only in the direction from the condenser to the electrode,and a manually operated switch for simultaneously controlling both thecondenser charging circuit and the ignitor circuit by permitting currentto flow from the condenser to the electrode only when the condensercharging circuit is open.

10. In an apparatus for magnetizing an article, a magnetizing coilaround the article, a condenser, a circuit. for charging the condenser,a mercury vapor switch connected in series with the condenser and coil,an ignitor electrode in said switch adapted to vaporize the mercury whencurrent is applied to the electrode, an ignitor circuit connecting thecondenser and electrode for supplying current to the electrode, arectifying tube in the ignitor switch to permit the flow oi current insaid ignitor circuit only in the direction from the condenser to theelectrode, a resistance across the magnetizingcoil to suppress back E.M. F. in the coil, and a manuallyoperated switch for simultaneouslycontrolling both the condenser charging circuit and the ignitor circuitby permitting current to flow from the condenser to the electrode onlywhen the condenser charging circuit is open.

11. In an apparatus for magnetizing an article, a coil around thearticle,'a condenser, a condenser charging circuit, a circuit fordischarging the condenser through the coil around the article, a mercuryvapor switch in the discharge circuit having therein an electrode tovaporize the mercury when current is applied to the electrode, anignitor circuit connecting the condenser and electrode for supplyingcurrent to the electrode, a manually controlled relay switch common tosaid condenser charging and mercury tube ignitor circuits, 9. pair ofcontacts. in said relay switch electrically connected respectively inthe charging and ignitor circuits, a relay armature electricallyconnected to the condenser,

and means for normally holding the armature against the ignitor circuitcontact and permitting the armature to engage the charging circuitcontact when the relay is energized.

12. In an apparatus for magnetizing an article, a coil around thearticle, a condenser, a source of alternating current, a relay switchhaving a pair of contacts and an armature therein for controlling theapparatus, a variable transformer having its primary winding connectedto said 'power source, a condenser charging circuit comprising thesecondary winding of said transformer, a rectifier tube, the condenser.one 01' the relay contacts and the relay armature in serics.=a circuitfor discharging the condenser through the coil. around the article, amercury vapor switch in the discharge circuit having therein anelectrode to vaporize the mercury when current is applied to theelectrode, an ignitor circuit connecting the condenser and electrodethrough the relay armature and the other relay contact for supplyingcurrent to the electrode, a spring in the relay adapted to normally holdthe armature against the ignitor circuit contact and permit the armatureto engage the charging'circuit contact when the relay is enersized. andmeans for energizing the relay from said power Source. 1

RALPH A. BRADER.

